1. Field of the Invention
The present invention relates to a system and method for detecting an operating mode of an internal combustion engine, particularly after a commanded mode transition, and controlling the engine based on the detected operating mode.
2. Background Art
Internal combustion engine technology is becoming increasingly more sophisticated and complex in an effort to achieve the optimal balance between performance, fuel economy, emissions, and cost. Rather than the historical approach of compromising design trade-offs when designing an engine to achieve certain performance characteristics under some limited operating conditions, current strategies often incorporate multiple engine operating modes that may alter control strategies or physical engine characteristics to improve performance under more operating conditions, with the ultimate goal of achieving optimal performance under all operating conditions. For example, different operating modes may be provided to alter valve timing, spark timing, air/fuel ratio, or compression ratio, for example, based on engine and ambient operating conditions including idle, part-throttle, full throttle, low load, high load, high altitude, low temperature, and high temperature, for example. The engine controller determines an appropriate operating mode and commands a mode transition based on the current or anticipated engine or ambient operating conditions.
The demands of customers and regulatory bodies alike dictate continuous and comprehensive monitoring of engine performance, and mitigation of performance degradations in individual components or entire systems during various operating modes. Additional sensors may be added to the system to more closely monitor engine operation and quickly and accurately diagnose anomalous operation of one or more interrelated components or systems. However, even if an appropriate sensor is available for use in monitoring a particular component or condition, adding sensors may unnecessarily increase the cost and complexity of the engine. For many applications, suitable sensors may not be available, due to packaging, cost, reliability, accuracy, or other considerations. As such, it is desirable to monitor and diagnose anomalous operation for various operating modes using existing engine sensors and/or actuators.
Variable compression ratio (VCR) internal combustion engines have been developed with one or more operating modes corresponding to lower and higher cylinder compression ratios to balance considerations for performance, fuel economy, and emissions for varying ambient and operating conditions. A number of implementations of VCR engines exist. One approach is to modify the connecting rod length using fluid pressure to adjust the position of the connecting rod and/or piston relative to the crankshaft to increase or decrease the effective piston stroke. To determine whether a particular cylinder is operating in a lower or higher compression ratio mode, cylinder pressure sensors, proximity sensors, accelerometers, and/or crankshaft position sensors may be used. However, this adds cost and complexity to the system with potential manufacturing and durability considerations. As such, for VCR engines, it is desirable to determine or detect whether one or more cylinders that have been commanded to change compression ratio operating modes has responded appropriately without requiring one or more additional sensors.